Korean J Radiol.  2016 Oct;17(5):598-619. 10.3348/kjr.2016.17.5.598.

Emerging Techniques in Brain Tumor Imaging: What Radiologists Need to Know

• Kim M
• Kim HS

• KMID: 2458052
• DOI: http://doi.org/10.3348/kjr.2016.17.5.598

Abstract

Among the currently available brain tumor imaging, advanced MR imaging techniques, such as diffusion-weighted MR imaging and perfusion MR imaging, have been used for solving diagnostic challenges associated with conventional imaging and for monitoring the brain tumor treatment response. Further development of advanced MR imaging techniques and postprocessing methods may contribute to predicting the treatment response to a specific therapeutic regimen, particularly using multi-modality and multiparametric imaging. Over the next few years, new imaging techniques, such as amide proton transfer imaging, will be studied regarding their potential use in quantitative brain tumor imaging. In this review, the pathophysiologic considerations and clinical validations of these promising techniques are discussed in the context of brain tumor characterization and treatment response.

Keyword

Brain; Neoplasm; Chemoradiotherapy; Perfusion; Diffusion; Magnetic resonance imaging

MeSH Terms

Brain Neoplasms/blood supply/*diagnostic imaging/physiopathology/therapy
Diffusion Magnetic Resonance Imaging/methods
Humans
Magnetic Resonance Imaging/methods/trends
Multimodal Imaging
Neovascularization, Pathologic/diagnostic imaging
Treatment Outcome

Figure

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  Fig. 1 Illustration of diffusion characteristics and their image processing Fast diffusion within extracellular and extravascular space is calculated by monoexponential fitting of diffusion signals with b values of 0 and 1000 s/mm2. Very rapid diffusion due to capillary perfusion can be characterized by biexponential fitting of diffusion signals as function of multiple b values, especially those less than 200 s/mm2. Intracellular slow diffusion can be determined by biexponential fitting of diffusion signals with multiple high b values. IVIM = intravoxel incoherent motion

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  Fig. 2 DWI with low and high b values of presumed lymphoma in 38-year-old male A. Contrast-enhanced, axial, T1-weighted MR image shows contrast-enhancing mass in brain stem. B. DWI with b value of 1000 s/mm2 shows equivocal high-signal intensity in same lesion. C. DWI with b value of 3000 s/mm2 enhances DWI signal, high signal intensity in corresponding lesion. D. ADC is correspondingly low as DWI with higher b values increases effect on signal of obstacles to free diffusion present in tissue. ADC = apparent diffusion coefficient, DWI = diffusion-weighted MR imaging

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  Fig. 3 Different DWI signals within tumor necrosis of two glioblastomas A. Necrotic tumor component of glioblastoma usually shows low DWI signal (arrow) due to migration and apoptosis of hypoxic tumor cells. B. Tumor necrosis could also show high DWI signal (arrow) due to tumor coagulation necrosis or ischemia associated with vascular occlusion by tumor cells. DWI = diffusion-weighted MR imaging

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  Fig. 4 Increased rCBV of anaplastic astrocytoma in 23-year-old male A. Intra-axial mass with high signal intensity seen on FLAIR, is noted in left frontal lobe. B, C. Mass dose not enhance on contrast-enhanced axial (B) and coronal (C), T1-weighted MR images. D. rCBV map derived from DSC perfusion MR imaging shows markedly increased rCBV in corresponding lesion, and thus reflecting larger luminal area of tumor microvessels. DSC = dynamic susceptibility contrast, FLAIR = fluid attenuated inversion recovery, rCBV = relative cerebral blood volume

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  Fig. 5 Images obtained in 63-year-old female clinicoradiologically considered as having recurrent glioblastoma A. Contrast-enhanced, T1-weighted image acquired 17 months after concomitant chemoradiotherapy, shows necrotic, enhancing mass in left parietal lobe. B. DSC perfusion MR image shows equivocal increase of rCBV in corresponding lesion. C. Corresponding, contrast-enhanced, solid portion shows definite increase of permeability on DCE perfusion MR imaging, and thus suggesting tumor recurrence. DCE = dynamic contrast-enhanced, DSC = dynamic susceptibility contrast, rCBV = relative cerebral blood volume

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  Fig. 6 Comparison of DSC and DCE perfusion MR images in 67-year-old female with glioblastoma A. Contrast-enhanced, axial, T1-weighted MR image shows necrotic, contrast-enhancing mass in left frontal and temporal lobes. B. DSC perfusion MR imaging shows heterogeneously increased rCBV in corresponding lesion. C. DCE perfusion MR imaging shows higher signal-to-noise ratio and spatial resolution of permeability distribution within same lesion, compared with that seen on DSC perfusion MR imaging. DCE = dynamic contrast-enhanced, DSC = dynamic susceptibility contrast, rCBV = relative cerebral blood volume

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  Fig. 7 Illustration of association between tumor vessel pattern and cerebral blood volume A. Immature, hyperpermeable, and tortuous tumor vessel pattern causes ineffective and heterogeneous tumor blood flow (arrow) which thus impedes delivery of chemotherapeutic drug to tumor. B. Increased homogeneity of tumor-vessel density and more well ordered arrangement of vessels increase tumor blood flow (arrow) and reduce its heterogeneity, and which improve drug delivery and efficacy. CBF = cerebral blood flow, DCE = dynamic contrast-enhanced

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  Fig. 8 Images obtained in 76-year-old male with glioblastoma A. T2-weighted MR image shows intra-axial mass with surrounding edema in right parietal lobe. B. DWI shows high signal intensity in corresponding lesion, and thus suggesting high tumor cellularity. C. Contrast-enhanced, axial, T1-weighted MR image shows necrotic, contrast-enhancing mass in same lesion. D. Contrast-enhanced SWI shows additional information regarding microhemorrhage and tumor microvessels around tumor necrosis seen on contrast-enhanced, T1-weighted image. DWI = diffusion-weighted MR imaging, SWI = susceptibility-weighted imaging

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  Fig. 9 Images obtained in 47-year-old male with anaplastic oligodendroglioma A, B. T2-weighted MR image (A) and contrast enhanced, T1-weighted image (B) show intra-axial lesion with internal hemorrhage in left frontal lobe. C. Pre-contrast SWI demonstrates rim of low signal intensity in corresponding lesion. D. Contrast-enhanced SWI shows additional linear or dot-like structures of low signal intensity (arrows), suggesting tumor microvessels as well as unchanged lesion of low signal intensity (arrowhead), and suggesting microhemorrhage. SWI = susceptibility-weighted imaging

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  Fig. 10 Illustration of amide proton transfer mechanism Amide protons are saturated at their specific resonance frequency with selective radiofrequency pulse. Saturated proton is then transferred to surrounding free water and consequently water signal decrease is calculated for indirect estimation of amount of amide proton.

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  Fig. 11 Images obtained in 55-year-old male with glioblastoma A. Contrast-enhanced, axial, T1-weighted MR image shows contrast-enhancing lesion around fourth ventricle. B-E. All of advanced MR images including DWI (B), DSC perfusion MR image (C), DCE perfusion MR image (D), and amide proton transfer image (E) show increased parametric values, although different distribution within corresponding contrast-enhancing lesion. DCE = dynamic contrast-enhanced, DSC = dynamic susceptibility contrast, DWI = diffusion-weighted MR imaging

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  Fig. 12 Images obtained in 57-year-old female with recurrent glioblastoma A. Contrast-enhanced, T1-weighted image acquired five months after concomitant chemoradiotherapy shows necrotic, enhancing mass in right temporo-occipital lobe. B, C. DWI (B) and ADC (C) show linear area of diffusion restriction surrounding tumor necrosis, possibly indicating viable, compact tumor cells. D. DCE perfusion MR image shows increase of permeability in corresponding, contrast-enhancing lesion around area of diffusion restriction, and reflecting immature tumor vessel. ADC = apparent diffusion coefficient, DCE = dynamic contrast-enhanced, DWI = diffusion-weighted MR imaging

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  Fig. 13 Images obtained in 55-year-old female with recurrent glioblastoma A. At seven weeks after concomitant chemoradiotherapy, histogram from normalized rCBV for entire, corresponding, contrast-enhancing lesion reveals heterogeneous distribution of normalized rCBV values. B. At 15 weeks after concomitant chemoradiotherapy, histogram showed more heterogeneous distribution of normalized rCBV values compared with those seen in previous study, and thus suggesting tumor progression. rCBV = relative cerebral blood volume

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  Fig. 14 Images obtained in 75-year-old female with pseudoprogression A. Contrast-enhanced, T1-weighted image acquired five weeks after concomitant chemoradiotherapy shows enhancing mass in right parieto-occipital lobe. B, C. ASL (B) and DCE perfusion MR imaging (C) show increased CBF and permeability in corresponding contrast-enhanced lesion, respectively, and thus indicating effective drug delivery. D. After two cycles of adjuvant temozolomide, extent of enhancing lesion increased. E. After four cycles of adjuvant temozolomide, enlarged, enhancing lesion was stabilized, and thus suggesting pseudoprogression. ASL = arterial spin labeling, CBF = cerebral blood flow, DCE = dynamic contrast-enhanced

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  Fig. 15 Tumor clustering in 59-year-old female with recurrent glioblastoma A. Contrast-enhancing mass is segmented and clustered with combination of ADC, rCBV, and permeability parameters on voxel-by-voxel basis. B. Volume fraction of presumed tumor cluster is highest (45%), compared with other clusters (C, D), and thus suggesting tumor recurrence. ADC = apparent diffusion coefficient, rCBV = relative cerebral blood volume

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